How To Clean A Cloudy or Very Dirty Pool

I often see a cloudy pool described on the Internet as “not very inviting” which is u huge understatement. My dear pool owners, let’s face it – a cloudy pool is an eyesore or simply gross. “How to clean a cloudy pool” is a question asked way too much which shows that people are not aware that “Why is my pool cloudy” is the question people should actually be asking.

If you ask the right question, you will find out how to prevent this from happening, which is way easier and less time consuming than dealing with a very dirty pool.

Still, we will go over the most common causes of cloudy water and give advice how to solve each problem.

Most common reasons of cloudy pool water are:

  1. low free chlorine levels
  2. heavy rainfall dilutes the water so free chlorine levels drop
  3. UV sun’s rays destroy free chlorine.

In any of the above cases, if your pool water is cloudy as a result of low free chlorine levels (which you should test first), you need to shock your pool immediately.

If it’s not about free chlorine and you are not certain what cause cloudiness and how to deal with it, we’ll try to figure it out together in this article.

We need to find out if the cause might be any of the following:

  1. Improper chemicals used and imbalanced poor water
  2. Faulty filter or inadequate filtering time
  3. Bad pool water circulation
  4. Environmental factors (debris, particles, vicinity of contminants)
  5. Pool shock short-term aftermath

Read to move on to diagnostics?

How to clean a cloudy pool

Wrong or Imbalanced Pool Chemicals

Chlorinated swimming pool chemistry (for saltwater pools check out our ultimate guide) needs to be approached with care and caution as wrong chemicals or incorrect amounts are the most common causes of cloudy water. Further complication might be algae infestation. If that happens, oh boy…

The most often causes of cloudiness are bad pH and chlorine levels. pH is not directly related to cloudiness in pool water, but when pH is imbalanced, it decreases free chlorine and makes it ineffective.

When free chlorine level drops, what forms is combined chlorine (chloramine). This turns the water cloudy and lowers efficiency in killing bacteria and algae.

In addition, pay close attention to changes in the level of total alkalinity (TA) using a reliable test kit. A high TA causes a few problems, including calcium scaling which is also associated with cloudiness.

You can lower total alkalinity when it gets out of the ideal range. You mainly have to check bicarbonate alkalinity and make sure it’s 80 ppm and 120 ppm. To decrease the alkalinity of pool water use muriatic acid or sodium bisulfate.

Suggested article: 6 Best Salt Water Chlorinator Reviews 2017

High levels of phosphate and bromine as well as cyanuric acid (CYA) can also cause cloudiness. If you are using cyanuric acid often, make sure that the CYA and free chlorine (FC) levels are balanced. Increased, levels of CYA will reduce free chlorine.

The more stabilizer you put in your pool to protect the chlorine from the sun, the more chlorine you will need to maintain its effectiveness.

Here’s the chart to follow:

A good test kit tests pH, free chlorine, combined chlorine, total chlorine, bromine, calcium hardness, total alkalinity, and cyanuric acid. Sometimes you’ll need several test agents.

Here’s a free pool chemistry calculator to make it easy for you to find the exact amount of each chemical to add.

How to Clear A Cloudy Pool If The Cause Is Chlorine Imbalance

In the ideal case, the recommended chlorine levels should be around 3 ppm. This value should be the same as the total chlorine if chloramine is at 0 ppm.

The wider the range between free and total chlorine, the more combined chlorine is present in the water. Combined chlorine should always read below 0.5 ppm or preferably 0 ppm. 

To achieve this, you will need test chlorine levels daily and adjust it as appropriate before there’s excess chloramine. For all outdoor pools, you can use chlorine stabilizer such as cyanuric acid which, as we mentioned, prevents chlorine depletion as a result of direct UV light.

Don’t forget that cyanuric acid is very strong and if it exceeds the recommended levels, free chlorine will be eaten up. As a result, the water will get cloudy and the risk of growing algae will increase.

If combined chlorine reads above 0.5 ppm, pool water will turn cloudy and become unsafe for swimming. If this is the case, you must shock your pool ASAP.

Monitoring pH and Total Alkalinity

The concentration of pH in the water affects how all the water’s chemicals function, including chlorine. When pH level gets too high, chlorine will become ineffective.

The correct level of pH in a swimming pool should be between 7.4 and 7.6.

To lower pH level, you need to use a pH reducer such as muriatic acid or sulfuric acid.

Anything below pH of 7.0 is way too low and will turn water cloudy. It might also bring about harmful bacteria and as algae. To control low pH levels, you need to use a pH Increaser such as soda ash.

Once again, make sure that total alkalinity is within the required range of 80 ppm and 130 ppm to avoid bringing up pH levels and causing calcium scaling.

What to do when all the chemicals are balanced but your pool water is still cloudy?

In such scenario, you probably have all sorts of unwanted particles in your pool.

You can use a water clarifier to collect all the fine particles so that they can be picked up by the filter. Alternatively, you can use pool floc (flocculant), also known as a super floc.

This is a chemical that is used to bring all the clouding particles to the bottom of your pool so that you can vacuum them up using a manual pump. The particles collected using a pool floc can’t pass through the filter’

Remember to make sure that your filter is set on the ‘Backwash’ or ‘Waste’ option when you are vacuuming. This will avoid any damage that may happen to the filter as a result of clogging.

What If the Swimming Pool Water Is Still Cloudy After Shocking?

Your water will probably look cloudy or milky-white after you have shocked your pool. This is a normal occurrence and the pool water will clear up soon. Make sure that your pump and filter are running properly for at least a day after shocking.

If the cloudiness doesn’t disappear 24 hours after shocking, you might have used less than stellar quality chlorine shock. Test free chlorine again and use a better quality chlorine shock.

You should also check that pH, total alkalinity, cyanuric acid, and calcium hardness are all within the recommended range.

Pool Filtration and Circulation Systems

Poor water circulation system can also be a huge problem. If your water cannot circulate and be filtered properly, it will become stagnant and cloudy.

Make sure that the return fittings are turned to point down in order to enable the water at the bottom of the pool to circulate properly. The circulation system will largely depend on how the pool was built in the first place.

Another thing to bear in mind is using the right pump size to adequately clean the water.

Make sure the filtration system is running long enough. A public pool filter should be running constantly for the water to remain clean all the time while for home pools 8 -10 hours a day will be long enough.

Inspect the filter carefully and remove particles that may be blocking the filter. Your filter system continuously cleans the water, and if it does not function properly, the water will be dirty, cloudy, and may even develop algae.

Large particles tend to block filtration systems, especially the diatomaceous earth (DE) and cartridge pool filters. Sand filters are not that sensitive to particles

Ensure that you regularly clean, backwash, and replace the cartridge or DE filter medium as appropriate. As for sand filters, make sure you check out are detailed article.

Check that your filter is in good condition. Any leaks will cause cloudiness:

How about algae?

Apart from inconsistent chlorination, one of the most common culprit which causes cloudy pool water is algae so read our article on how to deal with them. They appear due to poor sanitation and water circulation. If your pool is green and cloudy it’s probably because you have an algae issue that needs to be sorted out.

 In addition to living algae, your water may be cloudy because of the dead algae, too. Look for the grey or white cloudiness usually after using an algaecide or shock. 

They can be very difficult to remove especially if you have a sand or cartridge filter.

The environment and weather conditions

The environment and weather may also be the cause of cloudy water. Free chlorine depletes more quickly in full sunlight, so trees and buildings near your pool will block direct sun. However, flying debris from nearby trees and roofs will make your water dirty or contaminated so you will not get any help from sunlight obstacles if they are too close to the pool.

Other large and small foreign particles may find their way into the water, especially during spring and in windy weather throughout the swimming season.

Body oil used by swimmers accumulates in the pool causing cloudiness in most cases. You can use manual skimmers to remove visible particles or clarifier as well as pool flocculant before vacuuming your pool to get rid of fine particles and oily substances once they sink down to the bottom of the pool.

Heavy and prolonged rain also affects on your pool clarity so test all chemicals, especially chlorine, and adjust them as appropriate afterwards.

And remember, prevention is always better than the cure, so act accordingly!

Aleks Stanic

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